Officer Valadez Sr. was killed in the line of duty in 2009 when his son was only three weeks old.

The officers, along with the Chicago Police Memorial Foundation— a non-profit organization that honors the lives and supports the families of fallen heroes— proposed the idea to attend the graduation and make Alex's day unforgettable.

"He came out with the biggest smile on his face," CPMF volunteer, Kate McMahon, told InsideEditon.com. "We were all glad to be there."

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Cops stand by fallen officer's son at kindergarten graduation

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Cops stand by fallen officer's son at kindergarten graduation: 'We were all glad to be there'